In photo technique moving apertures (shutter, shutter apertures) for the dosage of the amount of light are known, whereby e.g. the breadth of the aperture for the variation of the amount of light can be differently adjusted.
In radiology, apertures are known as collimators which serve with constant dimensions for the reduction of the produced radiation dosage, but which, according to U.S. Pat. No. 4,773,087, also are used for the reduction of scattered radiation. Furthermore, collimators can be adjustable in order to, adjusted to the object to be recorded, limit the radiated area. In this way, it is shown in U.S. Pat. No. 4,122,350 a size-adjustable collimator for the limitation of the area impinged by rays in mammography, whereby no relative movement between the object and radiation source occurs. From U.S. Pat. No. 4,603,427, an adjustable collimator is known by means of which the height of the irradiated area can be limited in connection with cephalometric panorama photos. The breadth of the section of the ray beam and the slewing plane is determined by a non-adjustable slit at the exit of the radiation source. Perpendicular to the slewing plane, the ray beam is limited by the height-adjustable collimator, whereby signaling rods show the limitation of the height. From U.S. Pat. No. 3,518,435, an adjustable collimator is known, which limits the irradiated area depending on the film cassette size used. In connection with the type of recording shown, no relative movement between the object and the radiation source occurs. In general, it is known in radiology to use collimators for the limitation of the irradiated area and, prior to the real recording, to display the limited area for the control thereof on the object (patient) by means of visible light. Furthermore, collimators for the limitation of the X-rays are used when using line detectors such that the radiosensitive line detector is exclusively irradiated. In classic photographic radiology, radiation grids are also used for the reduction of the scattered radiation. However, this method for the reduction of scattered radiation also weakens simultaneously the wanted radiation so that, for the production of a high-contrast image, high dosages of X-rays have to applied. These radiation grids, which are between the object and the image, are constant in their dimensions. The absorption of undesired scattered radiation by the recording means during the image recording generally leads to a declined wanted signal/unwanted signal ratio and thus not to an optimal image quality.